The bomb hit the main gate of the Al-Zuhra hospital and maternity center in Pass Kalay, a town in the district of Hangu, said Abdul Rashid Khan, the police chief in Hangu. The hospital and mosque cater to Shia patients and worshippers.

The blast damaged the mosque, two houses and two vehicles, he said.

At least two children were killed.

Hangu sits next to Pakistan's tribal region and is part of a region plagued by sectarian violence between Sunnis and Shias.

The attack happened on the second day of Muhharam, one of the holiest days on the Islamic calendar, when violence and fighting is prohibited.